Hi! I wanted to play Holiday Hare '17 and I couldn't play level 1. When I play it it looks exactly the same as on the preview image where the zip file is:
This level can't be opened in JCS so I have downloaded MLLE in order to see it and there it looks fine. It contains all the tiles, all the layers, backgrounds, etc.

Can someone please help me out? I'm coming here from GOG where I have downloaded the game, and I have downloaded the latest JJ2+ version. All the other levels work fine with all the JJ2+ features.

Puzzling. Could you share a screenshot or two of how level 1 looks in-game to you? And maybe go into some more detail about what "all the JJ2+ features" working in the other levels means to you, so we can be sure there's no mistake that scripts are otherwise running?

I'm pretty sure that the dragon guardian himself is a JJ2+ feature. He works perfectly fine, all his attacks, effects, etc. In other levels there are presents, custom enemies, enemies from JJ1 Nippius (snowmen, penguins), and so on.

Hmm, it's hard to tell from the screenshot whether the level's script isn't running at all or only the part of it that loads tilesets. Have you tried reextracting all files from the HH17 zip to make sure you didn't exclude one by mistake?

So that kind of explains what's happening but not really why. For some reason, your JJ2+ is trying to include multiple files that are different versions of the same libraries and therefore conflict with one another.

HH17 does not include Jazz1Enemies.asc, only Jazz1Enemies v03.asc. It also does not include TrueColor v12.asc, only TrueColor.asc. (Truthfully I'm not even sure why you have a file called Jazz1Enemies.asc, because every upload on J2O uses either v03 or v04.) Nor, as far as I can tell, does HH17_level01.j2as reference either of those two non-included files. Yet it seems you've done something that makes JJ2+ want to include them anyway?